A colleague showed me today the email she got about my Calendar invite: it had been in Japanese.

I’ve received emails from Apple in Japanese before, for example about password resets, due to the fact that I registered my—then me.com—address while I’ve been living in Japan. I didn’t mind it much. However, in cases like above this behaviour might cause certain problems…

But what sets the language of service emails about Calendar invites or iMessage device activations? Apparently the language setting of the icloud.com website has nothing to do with it. A quick search pointed me to appleid.apple.com and sure enough it had a section called Language and Contact Preferences with the preferred language set to 日本語.